Discussion on How do you get your knee armor to sit properly? within the Boba Fett Armor forum, part of the Star Wars Original Trilogy Bounty Hunters category; This is how my knee armor sits. The bottom always
You have the elastic a little to high and it looks to be attached to the inside of the front of the armor. The tab sticking out behind the darts is where the elastic should be attached, at the outter edges. You also should push it down a little bit. the strap should be right behind your knee. In addition to repositioning the elastic, you can add velcro inside the front of the knee armor and on your jumpsuit. This will prevent them from falling/twisting. Hope that helped!